mm: numa: Create basic numa page hinting infrastructure

Note: This patch started as "mm/mpol: Create special PROT_NONE
	infrastructure" and preserves the basic idea but steals *very*
	heavily from "autonuma: numa hinting page faults entry points" for
	the actual fault handlers without the migration parts.	The end
	result is barely recognisable as either patch so all Signed-off
	and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with
	this version, I will re-add the signed-offs-by to reflect the history.

In order to facilitate a lazy -- fault driven -- migration of pages, create
a special transient PAGE_NUMA variant, we can then use the 'spurious'
protection faults to drive our migrations from.

The meaning of PAGE_NUMA depends on the architecture but on x86 it is
effectively PROT_NONE. Actual PROT_NONE mappings will not generate these
NUMA faults for the reason that the page fault code checks the permission on
the VMA (and will throw a segmentation fault on actual PROT_NONE mappings),
before it ever calls handle_mm_fault.

[dhillf@gmail.com: Fix typo]
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index b31cb7da0346..a1d26a98c655 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -159,6 +159,10 @@ static inline struct page *compound_trans_head(struct page *page)
         }
         return page;
 }
+
+extern int do_huge_pmd_numa_page(struct mm_struct *mm, unsigned long addr,
+                                  pmd_t pmd, pmd_t *pmdp);
+
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
 #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; })
@@ -195,6 +199,12 @@ static inline int pmd_trans_huge_lock(pmd_t *pmd,
 {
         return 0;
 }
+
+static inline int do_huge_pmd_numa_page(struct mm_struct *mm, unsigned long addr,
+                                        pmd_t pmd, pmd_t *pmdp)
+{
+}
+
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 
 #endif /* _LINUX_HUGE_MM_H */